GB703610A - Improved dynamic brake system for electric locomotives - Google Patents

Abstract

703,610. Control of D.C. motors. GENERAL MOTORS CORPORATION. Dec. 22, 1952 [Jan. 2, 1952], No. 32368/52. Class 38(3) [Also in Group XXXVIII] An engine E drives a compound wound generator G for supplying traction motors having series field windings F1-F4 and armatures A1-A4 respectively, the motors being adapted for series-parallel control. To institute rheostatic braking, the motor field windings are connected in series across the generator and the armatures of the motors are shunted across individual resistors BG1-BG4. At the same time, a shunt field winding SF of the generator is disconnected from its armature and is placed across resistor BG2 with reversed. polarity so that it now opposes a battery-supplied field winding BF of the generator G. Thus, when the vehicle is braked at high speeds, the motor armature currents are limited by decreasing the generator excitation together with that of the motors. This results in a braking characteristic which allows a close approach to the maximum braking effort throughout a wide speed range of the vehicle. The generator field winding BF is connected to a battery BAT in parallel with an auxiliary generator 26 and has a regulator rheostat 28 controlled by governor 31. A potentiometer arm 48 is set to a position corresponding to the desired degree of excitation of the winding BF, and, when the potential at point 41 exceeds that of the arm 48 by a predetermined amount, current passes through relay winding 37 and rectifier 43 so that a relay 36 closes contacts to energize an overriding solenoid 31a. This solenoid then acts through the governor to increase the effective resistance of the rheostat 28 and thereby reduces the potential at point 41 until the relay 36 is deenergized, reverse current flow through the relay being prevented by the rectifier. The shaft 32, which is spring-biased, then moves to decrease the resistance of the rheostat 28 and causes a recurrence of the above sequence. A substantially constant current is therefore supplied to the field winding BF for any given setting of the arm 48. The system may be included in each unit of a train of vehicles, couplers 50 connecting the train line conduits TLC of the various units. The setting of the potentiometer 45 may be made in only the leading unit, and in any subsidiary unit the potentiometer may be disconnected by opening a switch corresponding to switch 51.